Hydraulic damping means



United States Patent [72] Inventor Katsuhiko Iijima 40-1, Den-en Chofu Z-Chome, 0hta-Ku, Tokyo, Japan [21] Appl. No. 765,912 [22] Filed Oct. 8, 1968 [45] Patented Nov. 24, 1970 [32] Priority Oct. 17, 1967 [33] Japan [31] No. 42/66747 [54] HYDRAULIC DAMPING MEANS 6 Claims, 6 Drawing Figs.

[52] U.S.Cl 91/410, 91/437, 91/445, 91/447 [51] Int. Cl F15b 13/04, F15b 11/08 [50] Field of Search ..9l/410, 396 445, 437 Cursory, 447 Cursory [56] References Cited UNITED STATES PATENTS 1,956,758 5/1934 Ernst 91/410 3,396,635 8/1968 Darling 91/396 FOREIGN PATENTS 7/1923 Great Britain 91/410 ABSTRACT: A hydraulic system for hydraulically operated apparatus includes a control valve interposed between a source of fluid under pressure and a hydraulic actuator for effecting traversing of the hydraulic apparatus. A valve assembly is interposed between the control valve and the actuator and includes a cutoff valve controlling connection of the control valve to the actuator and operable to block flow of fluid to and from the actuator. This cutoff valve includes pressure-responsive check valves allowing fluid to flow in a reverse direction at a reversal point of the actuator. The cutoff valve is moved to its flow-blocking position by limit means, such as a cam or lever, operated by the actuator. This limit means operates the cutoff valve to block the flow at the limit of the desired range of traverse of the apparatus in either selected direction. A pair of pressure-responsive relief valves are interposed between the cutoff valve and the actuator and operate, responsive to the blocking action of the cutoff valve, to short circuit or interconnect the fluid lines leading to the actuator and thus to dampen the impact pressure due to abrupt deceleration of the actuator near its limiting position in either direction.

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Sheet 4 of4 M 'ENTOR QTSUHIRD HSlNfi ATTORNEY 5 HYDRAULIC DAMPING MEANS BACKGROUND OF THE INVENTION This invention relates to hydraulic damping means and, more particularly, to means for limiting the angular range of traverse of hydraulically operated apparatus or machines.

In a majority of conventional hydraulic backhoes, shovels, and the like, which can be traversed through a defined angle of less than 360, means limiting the angular range of traverse has generally been a simple mechanical stop or abutment installed in a stationary part of the apparatus and cooperable with an abutment on the rotatable part of the apparatus to control the range of angular movement or traverse. However, known limiting means of this type have the disadvantage in that the abutments or associated parts are liable to be damaged by the impact and the torque of the hydraulic actuator effective in the direction of the abutment and when the machine comes to a stop at the limit of its traversing movement.

Various means have been proposed to overcome these disadvantages, such as reducing the angular velocity of the machine adjacent its limit of traverse, to reduce the impact on the mechanical stops due to the inertia of the moving part of the apparatus, or increasing the strength of the mechanical stops or abutments and associated parts of the apparatus. The results have proven unsatisfactory due tothe lower working efficiency and the increased weight of the hydraulically operated machine. Furthermore, in excavation work in places adjacent walls or other obstacles, the conventional backhoe or shovel, not provided with adequate means to arrest its traversing movement when the movable part thereof ap- BRIEF DESCRIPTION OF THE DRAWINGS In the drawings: FIG. 1 is a perspective view of a hydraulic backhoe having a conventional mechanical stop or abutment on a stationary proaches such obstacles, is liable to be damaged by striking against such obstacles.

SUMMARY-OF THE INVENTION In accordance with the invention, hydraulic damping means are provided in the hydraulic system of hydraulic apparatus, such as backhoes, shovels and the like, to dampen the abrupt deceleration of a hydraulic actuator when the hydraulic fluid supply and return lines connected thereto are blocked by a cutoff valve. This cutoff valve is operable by an adjustable limiting means, such as a cam or lever, which, in turn, is operated by the hydraulic actuator. At or near the limit of the range of movement of the apparatus by the hydraulic actuator, the limiting means moves this cutoff valve to a position blocking flow of hydraulic fluid to and from the actuator. The cutoff valve includes pressure responsive valves operable, at the limit of movement of the apparatus in one traversing direction, to provide for flow of fluid through the supply and return lines connected to the actuator to move the hydraulic apparatus in the other direction of traverse.

A feature of the invention is the provision of pressureresponsive valve means, included in a valve assembly also including the cutoff valve, and interposed between the cutoff valve and the supply and return lines leading from the valve assembly to the actuator. These pressure-responsive valve means operate, responsive to blocking of the fluid flow by the cutoff valve, to interconnect the supply and return lines leading to the actuator to dampen the abrupt deceleration of the actuator resulting from blocking of flow of fluidto and from the actuator by the blocking action ofthe cutoff valve.

An object of the present invention is to provide limiting means for limiting the range of movement of components of hydraulic apparatus and which limiting means is free of the disadvantages oflimiting means hitherto used. I

Another object of the invention is to provide such a limiting means characterized in that it prevents damage to component parts ofthe hydraulic apparatus.

A further object of the invention is to provide such a limiting means including damping means operable, responsive to interruption of the flow of hydraulic fluid to and from the actuator, to short circuit the actuator to dampen the deceleration thereof.

part thereof to limit traversing movement of a movable part thereof;

FIG. 2 is a somewhat schematic diagram of a hydraulic system, embodying the invention, as applied to a backhoe which can be traversed through FIG. 3 is an enlarged sectional view of a hydraulic buffer valve shown in FIG. 2, illustrating schematically associated parts; and

FIGS. 4, 5 and 6 are views similar to FIG. 3, but illustrating different positions of the buffer valve.

DESCRIPTION OF THE PREFERRED EMBODIMENT FIG. 1 illustrates a conventional hydraulically operated backhoe having a stationary abutment, as indicated at x, limiting traversing movement of the movable part of the hoe.

Referring now to FIG. 2, which illustrates an embodiment of the invention, a hydraulic system for a hydraulically operated apparatus, such as a backhoe, includes a hydraulic fluid reservoir 1 having a suction filter at its outlet connected with a four-way control valve 5, for the backhoe, through a gear pump 3 and a pressure relief valve 4. Four-wayvalve 5 in cludes a plunger 6 for controlling the traversing direction of the backhoe. Other plungers are provided, indicated as three in number, for controlling other movements of the movable components of the backhoe. The plunger 6 is at one ergd of a movable piston of valve 5, and a spring 7, operatively associated with the opposite end of the movable piston, biases plunger 6 to the neutral position in which it connects a fluid supply line leading from pump 3 to a fluid return line connected to a filter 8 interposed in a return line leading to reservoir I.

The backhoe is illustrated as including a hydraulic actuator having a cylinder 9, for operating the bucket 12 of a backhoe or shovel. One end of cylinder 9 is pivotally connected to an arm 13 whose other end is pivotally connected to bucket 12. Another hydraulic'actuator includes a cylinder 10 receiving a piston which is pivotally connected to an extension rod 14 of the backhoe .or shovel. The opposite end of cylinder 10 is pivotally connected to a rotatable'pillar 15 to which one end of extension rod 14 is pivotally connected, the opposite end of extension rod 14 being connected to arm 13. A third hydraulic actuator includes a cylinder 11 pivotally connected, at one end, to extension rod 14, and a piston pivotally connected to I the arm 13 to operate the latter. Respective fluid flow lines 16- .I7, 18-49, and 20-21 connect cylinders 9, 10 and 11 with four-way control valve 5. V

A rotary hydraulic motor, of the rack-and-pinion type, is illustrated at 22. Motor 22, although shown separately for the convenience of illustration, is actually installed at the position 22', in FIG. 2, with its pinion shaft connected with the rotary pillar 15. A cam 23 is fixed to rotary pillar 15 and operates the plunger of a buffer valve 29 at the limit of traversing movement of the backhoe or shovel -in either direction, cam 23 being operatively connected with the pinion shaft of hydraulic motor 22. First fluid flow supply and return lines 24-25 connect'four-way control 5 to buffer valve 29, and second fluid flow supply'and return lines 26 and 27 connect buffer valve 29 to hydraulic motor 22. A return line 28 interconnects buffer valve 29 to the lower pressure part of the hydraulic system, such as to the hydraulic fluid reservoir 1.

FIG. 3 illustrates buffer valve 29 and hydraulic motor 22, the piston of hydraulic motor 22 being illustrated as substantially at the neutral position which corresponds to the midpoint of the rotary or angular stroke of motor 22. Cam 23 is fixed to the pinion shaft of motor 22, as illustrated by the chain line. Buffer valve 29 is a valve assembly including a cutoff valve having a plunger or piston 32 slidably guided in a passage extending through housing 30 of valve 29. One end of piston or plunger 32 has a roller 31 rotatably mounted thereon and maintained in rolling engagement with cam 23 by means of a compression spring 33 operatively associated with the opposite end of piston or plunger 32. Within its interior, plunger or piston 32 has a pair of check valves each including a respective valve body 35 or 37 and a respective biasing spring 36 or 38.

Housing 30 of valve 29 is further formed with passages or bores mounting a pair of pressure-responsive safety, relief, or

bypass valves each comprising a valve body 39 or 41 and an associated biasing spring 40 or 42. These safety or relief valves dampen the impact pressure caused by the rotary inertia of motor 22 and its connected parts at the instant fluid flow to and from motor 22 is interrupted by the cutoff valve including the plunger or piston 32. Valve body 30 is further formed with flow passages 43-50, which will be referred to more specifically hereinafter and which interconnect various parts of valve 29.

The operation will now be described. With the parts of buffer valve 29 in the positions indicated in FIG. 3, when the plunger 6 of control valve 5, shown in FIG. 2, is moved in the direction shown by arrow B, hydraulic fluid under pressure delivered from gear pump 3 is directed into the line 25 and from there into the valve 29. The hydraulic fluid entering valve 29 through line 25 flows through oil passages 45 and 48, shown in FIG. 3, and line 27 to hydraulic motor 22. The hydraulic fluid under pressure entering the motor 22 operates the piston thereof in a direction to rotate the pinion shaft counterclockwise, as shown by the solid line arrow. Cam 23 accordingly is also rotated counterclockwise, as shown by the solid arrow, so that piston or plunger 32 is gradually moved to the right by spring 33 in accordance with the angular rotation of cam 23.

Oil leaving motor 22 flows through line 26, oil passages 47 and 44, line 24 and the return line at the bottom of four-way valve (FIG. 2) through filter 8 to reservoir 1. When the angular displacement of motor 22 approaches its limit, plunger or piston 32 is moved further outwardly by spring 33, as shown in FIG. 4, and the connection between line 25 and passage 45, as well as the connection between oil passage 44 and line 24 is closed, thereby reducing the angular velocity of motor 22. As a result, there will be an impact pressure or surge in line 25 and in oil passages 47, 49, 43 and 44 due to the rotary inertia ofextension rod 14, arm 13, bucket 12, cylinders 9,10 and 11, and the other parts connected with rotary pillar 15.

However, this pressure can be directed into line 27 through pressure-responsive valve 41. As a result, motor 22 continues to rotate until equilibrium, between the hydraulic pressure as produced due to the rotary inertia of the machine and the hydraulic pressure determined by spring 42 of valve 41, is attained.

Thus, by properly adjusting the stroke of plunger 32 with respect to the angular displacement near the limit thereof, the throttling rate of plunger or piston 32 with respect to its stroke, and the biasing force of spring 42, the impact pressure produced by halting of the backhoe or shovel can be hydraulically damped. Thereby, the traversing movement of the machine can be stopped more smoothly than by a mechanical abutment or stop.

To initiate a reversetraversing movement, or a movement with clockwise rotation of the parts shown in FIG. 4, the plunger of four-way valve 5 is actuated in the direction indicated by arrow A in FIG. 2. Hydraulic fluid under pressure is then delivered into pipe 24 and forces open check valve 35 by overcoming the bias of the associated spring 36 mounted in plunger or piston 32. The hydraulic fluid under pressure reaches motor 22 through oil passages 43 and 47 and line 26, as best seen in FIG. 5. The oil return of motor 22 flows through pipe 27 and the oil passages 48 and 45, and opens valve 37 against the bias of its associated spring 38. After flowing through pipe 25 and four-way valve 5, the return flow passes through filter 3 into reservoir 1. By this operation, clockwise rotary movement is effected.

When the machine is halted at the limit of its clockwise angular displacement in traverse, plunger 32 is pushed slowly in thus slowly closing the hydraulic circuit from line 24 to oil passage 44 and the return circuit from line 24 to oil passage 44. In this case, also, the machine can be stopped in a smooth and shockless manner because of the release of the impact pressure into line 26 through the then opened pressureresponsive valve 39, as shown in FIG. 6.

To start counterclockwise rotation from the limit of the clockwise rotation, hydraulic fluid under pressure from fourway valve 5 enters pipe 25 to open check valve 37 in plunger or piston 32, and the hydraulic fluid flows through oil passages 46 and 48 in line 27 to motor 22 as in the manner previously described. The return flow from motor 22 flows through pipe 26 and oil passages 47 and 44, opening valve 35 in plunger or piston 32, and returns to reservoir 1 through pipe 24, four-way valve 5 and filter 3.

If the machine, such as the hoe or shovel, is halted at points other than its two limits of traverse, the stopping can also be effected without shock through operation of either the pressure-responsive valve 39-40, for traverse in the clockwise direction, and the pressure-responsive valve 41-42, for traverse in the counterclockwise direction, with flow through lines 24 and 25 being blocked due to plunger 6 of valve 5 being returned to the neutral position.

As set forth, traverse of the machine can be halted, without shock, by means of the hydraulic buffer valve controlled by a cam or lever, and such halting can be effected either between the limits of traverse or at the limits of traverse. Thus, when the damping means of the invention is applied in a backhoe or other hydraulic apparatus, the impact force effective on the apparatus is minimized so that service life of the apparatus can be prolonged and the efficiency thereof can be improved. Additionally, and because the apparatus can be halted at any arbitrary point within the defined range by preadjusting the shape of the cam, excavating work in places adjacent walls or other obstacles can be performed with greater safety and without damage to the apparatus due to careless operation. The mechanism of the invention can be used with good results with backhoes, shovels, jib cranes, and the like having rotary or reciprocating mechanism which requires minimum impact when being halted at the end or limit of a range of operation.

Iclaim:

1. In hydraulically operated apparatus having a hydraulic system including a source of fluid under pressure, at least one hydraulic actuator and a control valve, connected by first supply and the return lines to the source and by second supply and return lines to the actuator, controlling the direction and extent of movement of the apparatus by the actuator: means limitingthe range of such movement and comprising, in combination, a valve assembly interposed in said second supply and return lines between said control valve and said actuator; said valve assembly including a cutoff valve controlling connection of said control valve to said actuator and operable to block flow of fluid between said control valve and said actuator through said second supply and return lines; limit means operable by said actuator and operatively associated with said cutoff valve, said limit means, when said apparatus has moved through a predetermined range in a selected direction, operating said cutoff-valve to block said second supply and return lines to interrupt. hydraulic communication between said control valve and said actuator; and pressure-responsive valve means, in said valve assembly between said cutoff valve and the portions of said second supply and return lines connected to said actuator, and operable, responsive to such blocking action of said cutoff valve, to interconnect said portions of said second supply and return lines to dampen the abrupt deceleration of said actuator upon-such blocking action of said cutoff valve.

2. ln hydraulically operated apparatus, means limiting the range of movement thereof, as claimed in claim 1, in which said limiting means limitsthe angular range of movement of said apparatus in the traversing direction,

3. In hydraulically operated apparatus, means limiting the range of movement thereof, as claimed in claim 1, in which said actuator includes: a rotary output member; said limit means comprising a cam secured for rotation with said output member; said valve assembly including a valve body and'said cutoff valve including a piston axially reciprocable in a passage in said valve body; a follower member on one end of said piston engageable with said cam; and'a spring operatively associated with the other end of said piston and biasing said piston to maintain said follower member engaged with said cam.

4, in hydraulically operated apparatus, means limiting the range of movement thereof, as claimed in claim 3, in which said cam is angularly adjustable relative to said output member to preset the limits of the range of movement of said apparatus.

5. ln hydraulically operated apparatus having a hydraulic system including a source of fluid under pressure, at least one hydraulic actuator and a control valve, connected by first supply and return lines to the source and by second supply and return lines to the actuator, controlling the direction and extent of movement of the apparatus by the actuator: means limiting the range of such movement and comprising, in combination, a valve assembly interposed in saidsecond supply and return lines between said control valve and said actuator; said valve assembly including a cutoff valve controlling connection of said control valve to said actuator and operable to block flow of fluid through said second supply and return lines; limit means operable by said actuator and operatively associated with said cutoff valve, said limit means, when said apparatus has moved through a predetermined range in a selected direction, operating said cutoff valve to block said second supply and return lines; pressure-responsive valve means, in said valve assembly between said cutoff valve and the portions of said second supply and return lines connected to said actuator, and operable, responsive to such blocking action of said cutoff valve, to interconnect said portions of said second supply and return lines to dampen the abrupt deceleration of said actuator upon such blocking action of said cutoff block flow of fluid'through said second suppl valve; said valve assembly comprising a valve body; said cutoff valve comprising a piston mounted for axial reciprocation in a passage in said body and controlling flow of fluid between the portions of said second supply and return lines connected to said control valve and the portions of said second supply and return lines connected to said actuator, said piston having passage means normally interconnecting the two portions of said second supply and return lines; and a pair of springbiased, normally closed check valves in said piston and operable, when said piston is in the blocking position at each limit of movement of said apparatus, to establish flow of pressure fluid to said actuator and return of pressure fluid from said actuator, responsive to operation of said control valve to supply pressure fluid to a respective one of said second supply and return lines,

6. In hydraulically operated apparatus having a hydraulic system including a source of fluid under pressure, at least one hydraulic actuator and a control valve, connected by first supply and return lines to the source and by second supply and return lines to the actuator, controlling the direction and ex tent of movement of the apparatus by the actuator: means limiting the range of such movement and comprising, in combination, a valve assembly interposed in said second supply and return lines between said control valve and said actuator; said valve assembly including a cutoff valve controlling connection of said control valve to said actuator and operable to y and return lines; limit means operable by said actuator and operatively associated with said cutoff valve, said limit means, when said apparatus has moved through a predetermined range in a selected direction, operating said cutoff valve to block said second supply and return lines; and pressure-responsive valve means, in said valve assembly between said cutoff valve and the portions of said second supply and return lines connected to said actuator, and operable, responsive to such blocking action of said cutoff valve, to interconnect said portions of said second supply and return lines to dampen the abrupt deceleration of said actuator upon such blocking action of said cutoff valve; said valve assembly including a valve body; said pressure-responsive valve means comprising a pair of springbiased pressure-responsive valves each interposed in a respective one of said second supply and return lines and providing for flow of fluid through its associated second supply or return line; said body being formed with passage means interconnecb ing said second supply and return lines; said pressure-responsive valves normally closing said passages. 

